1. Field of the Invention
The invention relates to a fuel cap, for closing the opening of a filler neck connected to a fuel tank of automobiles, consists of a closure fitting into the opening of a filler neck and a handle integral with this closure.
2. Prior Art
To close the opening of a filler neck connected to a fuel tank of automobiles, a fuel cap is attached to the opening of a filler neck. The basic purpose of this fuel cap is to be removable easily as necessary for refilling while preventing what fuel of the tank leak out through the filler neck. Because of a seal ring is often used, to block any gaps between the fuel cap and the inner wall of the filler neck and thus to close the filler neck completely when the fuel cap is closed. Normally, a fuel cap comprises of a closure fitting into the opening of a filler neck and a handle integral with this closure, and a seal ring is applied to the closure.
Fuel caps are to be classified roughly in bayonet-type and screw-type. With a bayonet-type fuel cap, the closure is disengaged from the filler neck by the handle being turned through approximately 90xc2x0; thus opening and closing are easy. With a screw-type fuel cap, on the other hand, the handle is rotated through more than 360xc2x0 to unscrew the closure from the filler neck, and an ample sealing effect with respect to leaking out of fuel is obtained when the cap is closed.
In recent years, the view over environmental pollution becomes severe, and reductions of which not only in exhaust gas but also in gasoline vapor transpiring into the atmosphere from fuel (gasoline) have been demanded. On this viewpoint, the opening time of a fuel cap (from the beginning of opening to the fully opened) or the closing time (from the beginning of closing to the fully closed) are regarded as problems. For instance, in the case of the screw-type fuel cap, improvements to the problem of that, because the closing time and opening time are both long, the time for which gasoline vapor is allowed to transpire is to be longer, have been required.
On the other hand, with a bayonet-type fuel cap, it is favorable that the closing time and the opening time are both shorter than a screw-type fuel cap by reason of the turning range of the closure is narrow. However, by reason of the turning range of the closure is narrow, there is in apprehension of opening that the closure turns in reverse under the impact of an accident, and the sealing effect is deteriorative when lateral load impressed compared to a screw-type fuel cap. In addition, the advantage of easy opening and closing includes problem of that is possible to erupt fuel under a differential pressure between the internal pressure of the tank and atmospheric pressure. These shortcomings of bayonet-type fuel cap are good reasons for drawing that screw-type cap has been seen more often in the market in recent years.
A number of technologies for solving or ameliorating this problem associated with bayonet-type fuel cap has been proposed. Such proposals are found in, for example, the U.S. Pat. Nos. 5,480,055 and 5,794,806. In these, to prevent opening of the closure even under the impact of an accident, the turning range of the closure is set over 90xc2x0 to 360xc2x0 (normally 180xc2x0), and the handle idles to the closure within a range of fixed angle (about 90xc2x0) as from the beginning of opening (the idling range is called xe2x80x98lost motionxe2x80x99). However, the problem of which is possible to erupt fuel under a differential pressure between the internal pressure of the tank and atmospheric pressure has not been solved.
Accordingly, the present inventors conducted an investigation to find a structure, firstly, of which is not to transpire gasoline vapor while the fuel cap is opening, and secondly, a structure with a bayonet-type fuel cap, of which is not to erupt fuel under a differential pressure between the internal pressure of the tank and atmospheric pressure. In other words, the points of what should be achieved on a fuel cap are; (1) in the case of a screw-type fuel cap, the structure of which prevent to transpire gasoline vapor until the cap is fully opened while utilizing advantage of high sealing effect, and which is to secure a sealing effect even when the closure turns under an accidental impact; and (2) in the case of a bayonet-type fuel cap, the structure of which is to prevent eruption of fuel caused by a differential pressure between inside and outside of the tank and which is to secure a sealing effect even when the closure turns under an accidental impact; and furthermore, (3) the structure of which is to raise sealing effect when the fuel cap is closed and to reduce or prevent transpiration of gasoline vapor as normal state.
The present invention provides a fuel cap, for closing the opening of a filler neck connected to a fuel tank of automobiles, consists of a closure fitting into the opening of a filler neck and a handle integral with the closure, and mounts the upper and the lower seal rings individually on the closure at positionally apart from the other. The focus of the present invention is to raise sealing effect, and by using a plurality of seal rings, it is achieved to reduce or prevent gasoline vapor transpiring through the seal rings (rubbers).
The upper seal ring and the lower seal ring provide unequal sealing effects; the upper seal ring provides a high sealing effect when the fuel cap is closed as well as a seal ring used in prior arts, and the lower seal ring have a structure (cross-sectional shape) and a positional relationship to a filler neck in order to secure a sealing effect while opening or closing of a fuel cap.
As a structure (cross-sectional shape) for contributing to secure a sealing effect, the lower seal ring whose working differs from a seal ring used in prior arts, is to be a cross-sectional shape which consists of a ring base part fitted to the closure; an umbrella-shaped part provided extending with downward pitch from the ring base part toward the inner wall of the filler neck; and an elastic support part, provided at the edge of the umbrella-shaped part, for pressing against the inner wall of the filler neck. In other words, the cross-sectional shape of the lower seal ring consists of an added lip part provided extending with downward pitch from the elastic support part toward the closure. Moreover, the lower seal ring, to obtain a positional relationship to the filler neck properly, is provided by pressure welding to the contact surface which is formed as a substantially vertical cylindrical side face with a concentric and a substantially same diameter as the lower seal ring on the inside of the filler neck, at range scale of from the fully closed position up to when the closure is completely pulled out so as to be removed from the filler neck. For example, in the case of closing a fuel cap by screwing the closure into the filler neck, the contact surface is formed as a substantially vertical cylindrical side face with a concentric and a substantially same diameter as internal threads on the inside of the filler neck; due to the lower seal ring is force to pass through the internal thread of which is formed inside of the filler neck.
This lower seal ring provides a sealing effect with pressure welding of the elastic support part to the inner wall of the filler neck, i.e. the contact surface. Besides, (a) there is no deterioration in sealing effect with pressure welding of the elastic support part to the inner wall of the filler neck when the closure leans under impact from outside. Even if the elastic support part were to detach from the inner wall of the filler neck, the portion of pressure welding to the inner wall of the filler neck is settled between the elastic support part and the lip part. Moreover, the passage of gasoline vapor and fuel is physically blocked as well as sealing effect; even (b) when an internal pressure of the tank greater than atmospheric pressure acts from the inside, or (c) when fuel almost erupts under the internal pressure of the tank, the pressure of gasoline vapor or fuel pushes open the umbrella-shaped part from below, and the portion of pressure welding to the inner wall of the filler neck is settled between the elastic support part and the lip part. The lower seal ring is also available as being a check-valve.
In the case of that the present invention is applied to a screw-type fuel cap, the structure of the upper seal ring and the lower seal ring mounts individually on the closure at positionally apart from the other so that the upper seal ring is ordered unsealing state after the beginning of which the closure is rotated, the lower ring is ordered unsealing state on the verge of the closure is deviated from the opening of a filler neck. In the case of that the present invention is applied to a bayonet-type fuel cap, the structure of the upper seal ring and the lower seal ring mounts individually on the closure at positionally apart from the other so that the upper seal ring is ordered unsealing state after the beginning of which the closure is rotated, the lower ring is ordered unsealing state on the verge of the closure is deviated from the opening of a filler neck. In a screw-type fuel cap, the outer diameter is assignable by which the lower seal ring comprises the outer diameter passing through the internal thread on the inner wall of the filler neck wherein screwing the external thread on the closure, and also comprises the outer diameter pressing contact with the inner wall of the filler neck below the internal thread.
Of course, the invention is also applicable to a bayonet-type fuel cap (of an improved type) wherein there is no lost motion in the closing direction but a predetermined angle of lost motion within the turning range in the opening direction, thereby, the issue of fuel erupting under internal pressure of the tank is resolvable. In this bayonet-type fuel cap, the outer diameter of the lower seal ring is assignable by which the lower seal ring comprises the outer diameter passing through the engagement ring on the inner wall of the filler neck wherein engaging the engagement projection on the closure, and also comprises the outer diameter pressing contact with the inner wall of the filler neck below the engagement ring.
The lower seal ring is favorable to conform to these outer diameter conditions and to be the cross-sectional shape consisting of a ring base part, an umbrella-shaped part, an elastic support part and a lip part as mentioned above, and to set an optimum detached locational relationship to the upper seal ring by the relationship of contact surface which is formed in the filler neck.